The matured sap is filtered and then stirred, first at room temperature then at 20-45 °C in a specially designed open vessel. The conclusion of the stirring is determined by the changing colour and viscosity of the sap under treatment. The refined urushi produced by this process has a much reduced water content and an appropriate viscosity for coating. During the processing, several important things happen:
In practice different grades and qualities of lacquer are prepared for use at different stages in the application process.
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